Merge pull request #1684 from dotty-staging/fix-1672

Fixed #1672: Add regression test.

Author: liufengyun

tests/neg/i1672.scala

@@ -0,0 +1,7 @@
+
+class Test {
+  implicit def compareComparables[T](x: T)(implicit ord: Ordering[T]) = // error: result type of implicit definition needs to be given explicitly
+    new ord.Ops(x)
+  class Bippy { def compare(y: Bippy) = util Random }
+  () < () // error: value `<` is not a member of Unit
+}